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.\" Copyright (c) 2025 iXsystems, Inc.
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.Dd May 6, 2025
.Dt ZFS-REWRITE 8
.Os
.
.Sh NAME
.Nm zfs-rewrite
.Nd rewrite specified files without modification
.Sh SYNOPSIS
.Nm zfs
.Cm rewrite
.Oo Fl Prvx Ns Oc
.Op Fl l Ar length
.Op Fl o Ar offset
.Ar file Ns | Ns Ar directory Ns …
.
.Sh DESCRIPTION
Rewrite blocks of specified
.Ar file
as is without modification at a new location and possibly with new
properties, such as checksum, compression, dedup, copies, etc,
as if they were atomically read and written back.
.Bl -tag -width "-r"
.It Fl P
Perform physical rewrite, preserving logical birth time of blocks.
By default, rewrite updates logical birth times, making blocks appear
as modified in snapshots and incremental send streams.
Physical rewrite preserves logical birth times, avoiding unnecessary
inclusion in incremental streams.
Physical rewrite requires the
.Sy physical_rewrite
feature to be enabled on the pool.
.It Fl l Ar length
Rewrite at most this number of bytes.
.It Fl o Ar offset
Start at this offset in bytes.
.It Fl r
Recurse into directories.
.It Fl v
Print names of all successfully rewritten files.
.It Fl x
Don't cross file system mount points when recursing.
.El
.Sh NOTES
Rewrite of cloned blocks and blocks that are part of any snapshots,
same as some property changes may increase pool space usage.
Holes that were never written or were previously zero-compressed are
not rewritten and will remain holes even if compression is disabled.
.Pp
If a
.Fl l
or
.Fl o
value request a rewrite to regions past the end of the file, then those
regions are silently ignored, and no error is reported.
.Pp
By default, rewritten blocks update their logical birth time,
meaning they will be included in incremental
.Nm zfs Cm send
streams as modified data.
When the
.Fl P
flag is used, rewritten blocks preserve their logical birth time, since
there are no user data changes.
.
.Sh SEE ALSO
.Xr zfsprops 7 ,
.Xr zpool-features 7
